1. Field of the Invention
The invention relates to a device for eliminating curl of a roll of recording paper for use in an image forming apparatus such as a facsimile apparatus or a copying machine, where image formation is carried out while drawing the recording paper from the roll.
2. Description of the Related Art
A curl eliminating device is disclosed in Japanese Patent Publication No. Hei 1-57019, where a roll of paper is folded in a direction opposite to a curling direction by utilizing tension to eliminate the curl.
Although the tension applied to a roll of paper is set constant, the magnitude of force exerted on the curl eliminating device is changed because the dead load of the roll of paper is changed depending on the amount of the roll of paper remaining. Namely, if the remainder of the roll of paper is large, the dead load of the roll of paper is large so that the force exerted on the curl eliminating device is also large. On the other hand, if the remainder of the roll of paper is small, the dead load of the roll of paper is small and, consequently, the force exerted on the curl eliminating device becomes smaller than that in the case where there is a large remainder of the roll of paper. It follows that the curl eliminating device cannot be operated with an adequate force all the time, with attendant problems that satisfactory curl elimination is inhibited due to a change in the force, and that curl, far from being eliminated, is also caused in the opposite direction for a part of the roll.
Also among devices for eliminating curl of recording paper, one type is proposed by applicant in Japanese Laid-Open Patent Publication No. 4-32453, which has not yet been examined, wherein the curl eliminating device is provided on a recording paper feed path, which extends from the upward rear edge of a substantially semi-cylindrical recording paper tray having an upward opening to an image recording unit, formed in a main body case of a facsimile apparatus. The curl eliminating device comprises a support roller and a curl eliminating plate having a downward curved projection disposed close to the support roller, wherein the recording paper discharged from the recording paper tray is passed through a V-shaped path, viewed from the side, in a direction opposite to that of the curl of the recording paper, thus eliminating the curl.
The curl eliminating plate disposed in the curl eliminating device is fixed to an upper cover member, which is turned openably, and the support roller is disposed on a side of the main body case. Accordingly, the curl eliminating plate is separated from the support roller when the upper cover member is opened in order to supply the recording paper to the recording paper tray, thereby contributing to convenience.
To sufficiently eliminate the curl, it is desirable to bring the curl eliminating plate into close contact with the circumferential surface of the support roller. However, it is not possible to do so as they will interfere with one another.